1. Field of the Invention
The present invention relates to the creation of an analysis model of an elastomeric material member with a strong nonlinearity, more particularly relates to the creation of an analysis model of an elastomeric material member with a strong nonlinearity gripped between a first member and second member.
2. Description of the Related Art
Mobile devices and other electronic devices are made waterproof or dustproof by forming the housing containing the electronic circuits etc. by a top member and a bottom member sealed airtight by rubber or another seal member. In this case, the rubber member is gripped between the top member and bottom member and held deformed. The thus deformed and held rubber member has to be suitably selected in accordance with the location where it is placed. Therefore, in the past, attempts have been made to analyze the rubber member etc. by numerical simulation using the finite element method.
In the conventional finite element method, the rubber member was divided into tetrahedral, pentahedral, or hexahedral solid elements to create a model, an approximation formula expressing the physical properties of the rubber was found from test data of the rubber member, and the approximation formula was used to define the material of the rubber member. However, a rubber member is a superelastomer with a nonlinear relationship between the stress and strain. Further, it sometimes is crushed or stretched to its limit by just a slight load. Further, there was the problem of a poor convergence of analysis by the approximation formula found. As a result, work such as changing the parameters became necessary and therefore time was taken until reaching a solution. Further, the range able to be approximated by an approximation formula was narrow. While matching with physical properties of an actual rubber member at one part, there was no longer a match if a little away from that part and therefore there was the problem that the precision of approximation became poor.
Note that evaluating a rubber or other material by simulation is known (see Japanese Patent Publication (A) No. 2005-121535, Japanese Patent Publication (A) No. 2005-121536, Japanese Patent Publication (A) No. 2006-138810, and Japanese Patent Publication (A) No. 2002-365205), but in each case, a solid model matching with the model shape was created when creating a model.